1. Field of the Invention:
The present invention generally relates to a head positioning system to aid in the accurate, planar visualization of temporomandibular joint structures. More particularly, the present invention relates to a head positioning and alignment device which provides a fixed, reproducible geometry of a patient's head with reference points from which precise positioning of the TMJ structure may be made possible. The present device also provides for accurate head positioning to facilitate cephalometric measurement using MR imaging.
2. Description of the Prior Art:
Internal derangement of the temporomandibular joint (TMJ) is an abnormal relationship between the mandibular condyle and the disc (meniscus). TMJ disease has been reported in random surveys to range in prevalence from 28 percent to 37 percent of the general population. It is myofacial pain dysfunction (MPD). This dysfunction, if left untreated, may progress to degenerative joint disease (osteoarthritis) involving the condyle, disc and glenoid fossa.
Patients afflicted with osteoarthritis usually complain of joint pain principally in the region of the posterior of the condylar, head, neck and tragus of the ear. These areas coincide with the anatomical position of the bilaminar zone of the TMJ. Surgical management of osteoarthritis usually consists of a meniscoplasty or meniscectomy with or without osseous recontouring.
The patient's medical history as well as clinical and diagnostic imaging examinations are extremely important in the establishment of a definitive diagnosis of any dysfunction. This history may include an episode of trauma, which can be a result of either a direct jaw injury or a "whiplash" type of injury. However, in many cases there is no history of trauma and the first sign of an internal derangement is a painless "click" in the joint during opening. Ultimately this condition progresses to crepitation in the joint which could be indicative of a disc perforation and/or degenerative joint disease.
Radiodiagnosis is an essential tool in determining the morphology and structural changes occurring in the temporomandibular articulation. As compared to other articular joints, the articulation is exceptional because of its unique anatomic configuration and complicated function. TMJ anatomy is complex and includes tortuous bony surfaces and intricate soft tissue configurations.
The multiple densities of the articulation and the variable shape of its components have emphasized the need for standardized radiographic techniques that will provide accurate and repeatable images of the structures of interest on a gross recording medium. The preferred radiographic technique, therefore, must provide images of articulation in different planes, as well as providing images produced at different sessions for comparison and evaluation. The contemporary technique to accomplish these goals is tomography.
A variety of methods have been proposed to describe the positioning of the patient's head for tomographic examination of temporomandibular articulation. Both Shore, Oral Surg, Oral Med, Oral Pathol, Vol. 13, pp. 341-350 (1960) and Baker, Radiol. Clin. North Am., vol. 14, pp. 105-127 (1976) have proposed that the average condyle angulation should be established at 20.degree. in the horizontal plane. Other investigators as well have suggested an individualized technique of head positioning for the articulation examination in which the angulation of the horizontal condyle axis may be determined from the submental vertex radiograph of the subject's head.
In order to develop a technique of corrected lateral cephalometric and corrected antero-posterior cephalometric tomography of the articulation, however, a cephalometric device is needed to allow the patient's head to be positioned according to the previously determined horizontal and vertical angles of each condyle. Preferably, this device should have at least two measurable degrees of freedom. Further, such a device should be capable of measuring and reproducing a desired jaw position in a given patent.